Drug-smuggling arch criminal gets stretch (5)
I believe the answer is:
reach
'stretch' is the definition.
(I know that stretch can be written as reach)
'drug-smuggling arch criminal' is the wordplay.
'drug' becomes 'e' (E is another name for ecstasy).
'smuggling' means one lot of letters goes inside another (inserted letters are smuggled in).
'criminal' indicates an anagram.
'arch' anagrammed gives 'rach'.
'e' inserted within 'rach' is 'REACH'.
'gets' acts as a link.
(Other definitions for reach that I've seen before include "Stretch of river: achieve" , "Arrive at - stretch of river" , "Extend an arm" , "Arrive at the destination" , "Put out the hand for a part of the river" .)